Just saw this thread and I would like to jump in to get some additional thoughts. I am planning a trip for next March. I currently have a 5D Mark III as well as a 100-400, 70-200 2.8 IS, 24-70L, and 17-40L.

Given my trip is almost a year out the plan is to rent a 7D (assume Mark II by then) and the new 100-400 f4 with built in tele (again assuming it is out by then). Lot of good advice from these threads on keeping the lens in place and what body to use where. For those that felt the exitisting 100-400 was limiting (reach/speed) what are your thoughts on this new lens in term of reach/speed/weight (I heard it is heavy). Would you put it on the 7D as it would also give the 1.6 factor or the 5D and rely on full frame and cropping in post production?

One other question on gear - Flash. I have seen some photos where they add flash and an attachment buy I would be concerned I would be checking the photos too often, as opposed to multiple shots". Using this type of attachment as a fill would be new and I would be afraid of not exposing my shots correctly and missing many.

My other questions surround what tour company to use and should I go on one specifically labeled photo-safari. I know some people prefer self-directed tours but I am not interested in that. I have been focused on a tour company, www.thomsonsafaris.com, as I had read a few good reports about them and they offer regular safari as well as photo safari. I did a little research on their photo guides and all I could find were good reviews.

I am very excited about this trip and just trying to get as many opinions as possible.